A wireless power transmission technology is a technology that wirelessly transmits power between a power source and an electronic apparatus. As one example, by using the wireless power transmission technology, a battery of a mobile terminal can be charged only by putting a mobile terminal such as a smart phone or a tablet on a wireless charging pad to provide higher mobility, convenience, and safety than a wired charging environment using the existing wired charging connector. The wireless power transmission technology attracts public attention to substitute for the existing wired power transmission environment in various fields such as medical treatment, leisure, a robot, and the like, which include home appliances and an electric vehicle afterwards in addition to wireless charging of the mobile terminal.
The wireless power transmission technology can be classified into a technology using radiation of an electromagnetic wave and a technology using an electromagnetic inductive coupling phenomenon and since the technology using the radiation of the electromagnetic wave has a limit in efficiency depending on radiation loss consumed in air, the technology using the electromagnetic inductive coupling phenomenon has been primarily researched in recent years.
The wireless power transmission technology using the electromagnetic inductive coupling phenomenon is generally classified into an electromagnetic inductive coupling scheme and a resonant magnetic coupling scheme.
The electromagnetic inductive coupling scheme is a scheme that transmits energy by using current induced in a coil at a receiving side due to a magnetic field generated at a coil at a transmitting side according to electromagnetic coupling between the coil at the transmitting side and the coil at the receiving side. The wireless power transmission technology of the electromagnetic inductive coupling scheme has an advantage that transmission efficiency is high, but has a disadvantage that a power transmission distance is limited to several mm and the wireless power transmission technology is very sensitive to matching of the coils, and as a result, a degree of positional freedom is remarkably low.
The resonant magnetic coupling scheme as a technology proposed by Professor Marine Solarbeach of MIT in 2005 is a scheme that transmits energy by using a phenomenon in which the magnetic field concentrates on both ends of the transmitting side and the receiving side by the magnetic field applied at a resonance frequency between the coil at the transmitting side and the coil at the receiving side.
As a result, the resonant magnetic coupling scheme is expected as the wireless power transmission technology that can transmit energy up to a comparatively long distance from several tens of cm to several m and simultaneously transmit the power to multiple apparatuses as compared with the magnetic inductive coupling scheme to implement authentic cord-free.